GB1382801A - Electrostatic spray coating - Google Patents

Abstract

1382801 Electrostatic spraying NAUCHNO-ISSLEDOVATELSKY INSTITUT SANITARNOI TEKHNIKI MINISTERSTVA PROMYSHLENNOSTI STROITELNYKH MATERIALOV SSSR 17 Jan 1972 2181/72 Headings B2F and B2L In electrostatic spraying a finely dispersed charged aerosol cloud 7, Fig. 1 is enveloped by a sheath 8 of ionised gas to assist its movement towards an earthed article 1 being sprayed and allow even coating of concavities thereof. The sheath is produced in the outer region of a corona discharge initiated by needle electrodes 9 electrified by an H.T. rectifier 5 the gas e.g. air being supplied through fish-tail nozzles 10 alternating the electrodes in a circumferential ring. The spray gun comprises a rotary head 3, Fig. 2, having helically-arranged nozzles 6, to abrasion resistant tips 17 of which spray material is supplied through a copper tube 4, also electrified by the rectifier 5, and in which it is charged by contact therewith. Air, supplied through a chamber 13 in which it is ionised by electrodes 12 on the tube 4, entrains and atomises the spray material as the air flows around the tips 17. In a modification, Fig. 3 (not shown), the gun has a hemispherical front end surface with which the tips (17a) are flush. The gun is mounted on rails 33, Fig. 4, and its movement is controlled by limit switches 36/5, 36/6, whilst the article 1 to be sprayed is under the control of limit switches 36/1 to 36/4 on an earthed conveyer 11. Remote or automatic control can be effected by an electrical system described in detail (Figs. 5, 6, not shown). The spray material is supplied from a container 24 mounted on H.T. insulators 26 and electrified from the rectifier 5 via a line 23, the container being pressurised by an air hose 28/1 and supplying the spray head 3 or 3a through a line 29 incorporating a metering device 27 under the control of the electrical system. Air hoses 28/2, 28/3 supply the head 3 or 3a and the nozzles 10 respectively. The head 3 or 3a is rotated by a drive mechanism 21, also controlled by the electrical system.